4 Machine Instructions Free Online FlashCards

What is a machine instruction?

A binary-coded command that a processor can interpret and carry out.

What does an instruction set architecture define?

An instruction set architecture (ISA) defines the instructions a processor supports, their meanings, and how their bits are organized.

What does an instruction format describe?

It divides an instruction’s bits into fields, such as an opcode, register fields, and operand or address information.

What does an opcode identify?

The opcode identifies the operation the instruction requests, such as addition, loading data, or branching.

What information do register fields provide?

They identify the registers used as sources or destinations for an instruction.

What is an immediate operand?

An immediate operand is a value written directly into the instruction, rather than fetched from data memory.

Where is the operand in register addressing?

The operand is held in a named CPU register.

How does direct or absolute addressing locate an operand?

The instruction contains the memory address where the operand is stored.

How does register-indirect addressing find an operand?

A register holds the memory address of the operand. For example, if R3 contains 1000, a load using (R3) reads from that location.

How does base-plus-offset addressing calculate an address?

It adds an offset to a register value to calculate a memory address; for example, 8(R3) means the address in R3 plus 8.

How does PC-relative addressing determine a branch target?

It calculates a branch target relative to the program counter, often using a signed offset, supporting branches to nearby instructions.

What is an effective address?

The final memory address calculated by an addressing mode.